<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <title>效率测试</title>

</head>

<body>

</body>

<script>
  function fn() {
    var d1 = +new Date();

    for (var i = 0; i < 1000; i++) {
      var div = document.createElement('div');
      div.style.width = '100px';
      div.style.height = '2px';
      div.style.border = '1px solid red';
      document.body.appendChild(div);
    }
    var d2 = +new Date();
    console.log(d2 - d1);
  }
  fn();
</script>

</html>